Inkjet printers have become increasingly popular for use in printing high quality text and image documents. In an inkjet printer, a printhead 100 includes an array of nozzles 102 as shown in FIG. 1. In operation, the printhead 100 moves across a surface of a printable medium (not shown) such as a sheet of paper with the array of nozzles 102 adjacent the surface of the paper. While the printhead 100 moves across the surface, control circuitry (not shown) controls each of the nozzles 102 to selectively spray or eject tiny droplets of ink onto the surface of the paper. The tiny droplets of the ink are selectively ejected from the nozzles 102 and deposited on the surface of the paper to form the desired text or images on the paper.
FIG. 2 is a simplified cross-sectional view of a single one of the nozzles 102 of FIG. 1. The nozzle 102 includes walls 200 and 202 that form a chamber 204 having an input aperture 206 into which ink from an ink reservoir (not shown) is supplied, as indicated by an arrow 208. Each nozzle 102 further includes a heating element or resistor 210 contained in the chamber 204. In operation of the nozzle 102, ink from the ink reservoir first flows into the chamber 204 of the nozzle. Control circuitry (not shown) then applies an electrical current to the resistor 210, causing the resistor to heat up which, in turn, heats up the ink contained in the chamber 204. As the resistor 210 heats up the ink in the chamber 204, a bubble 212 is formed in the ink along a surface of the resistor. The bubble 212 grows larger as the resistor 210 continues heating the ink, until at some point the bubble becomes so large that a tiny droplet of ink is sprayed or ejected from an output aperture 214 of the nozzle 102, as indicated by an air row 216.
FIG. 2 shows a surface 218 of a droplet that is being formed as ink is partially forced through the output aperture 214 in response to the growing bubble 212, with the droplet being ejected from the nozzle once the bubble reaches a sufficient size. In place of the resistor 210, some conventional nozzles 102 include a piezoelectric element. The piezoelectric element changes shape in response to an applied electrical signal to thereby apply pressure to the ink in the chamber 204 and eject a droplet of ink from the chamber via the output aperture 214.
From the above description of the printhead 100 and array of nozzles 102, it is seen that each nozzle must include as individual resistor 210 (or piezoelectric element) to spray or eject ink droplets from the nozzle. As a result, suitable conductive traces (not shown) must be routed to each nozzle 102 in the array and coupled to control circuitry (not shown) that controls the application of an electrical current to each resistor 210 via these conductive traces. The array may include hundreds or even thousands of nozzles 102 and the corresponding number of required conductive traces must of course be formed.
The array of nozzles 102 and required conductive traces are typically formed using conventional processing techniques that are utilized in manufacturing semiconductor integrated circuits. For example, various layers of silicon, oxide, and other materials may be formed, etched, and otherwise processed on a silicon substrate to form the chambers 204, chamber walls 200, 202, input aperture 206, output aperture 218, resistor 210, and any other components required for forming the nozzles 102. The output apertures 218, for example, are typically laser drilled holes that are formed in much the same way as through-holes or vias are formed during the manufacture of integrated circuits. These overall processing steps, including in particular the laser-drilled holes that form the output apertures 214 and the resistors 210 and associated conductive traces, make the formation of the conventional printhead 100 relatively expensive.
There is a need to simplify the construction of and lower the cost of inkjet printheads.